1. Field of the Invention
This invention relates to a memory unit, and more particularly, a memory unit with a voltage passing device.
2. Description of the Prior Art
An electrically rewritable nonvolatile memory is a type of memory that retains information it stores even when no power is supplied to memory blocks and allows on-board rewriting of a program. Due to the wide range of applications for various uses, there is a growing need for a nonvolatile memory to be embedded in the same chip with the main circuit, especially for personal electronic devices having strict requirement for circuit area.
A nonvolatile memory cell of prior art comprises one floating gate transistor for retaining data, and one or two select transistors for enabling the floating gate transistor to perform corresponding operations. Since all operations of the memory cell, including the program operation, the erase operation, the inhibit operation, and the read operation, are all controlled by the select transistors. Namely, the select transistors may have to operate with high voltages, and should be made of transistors with high threshold voltages.
However, due to the high threshold voltages of the select transistors, the read operation of the memory cell will require high voltage, which may slow down the reading process and cause unnecessary power consumption. Therefore, how to increase the reading process and reduce the reading voltage requirement has become an issue to be solved.